Hillside Stream Restoration Underway

One of the worst water and pollution problems in Greenbelt may soon be solved, thanks to a major project, costing at least $429,750, now underway near the Hillside Road Underpass.

The large concrete pipes for the headwall arrived on a long flatbed truck about 8 a.m. on Monday, October 17, 2011.

Terri Hruby, Greenbelt's Assistant Planning Director and project manager, explained that the headwall is a white concrete structure with side wings on either side of a hole for the pipe that will carry a stream under Hillside Road.  On Tuesday morning, pipes were still sitting on the steep slope between Hillside Road and the small creek that flows toward Greenbelt Lake as a natural stream until it reaches a long concrete culvert that begins right at the bridge to Fayette Place, which is construction headquarters.  The project stops there.

Hruby said the old headwall and pipes had deteriorated and a concrete chute that used to carry rainwater from Hillside Road to the stream had completely fallen apart.  This exposed the hillside to erosion, carrying sediment and attached chemicals to the stream and to Greenbelt Lake.

This results in more frequent lake dredging, Hruby said.

Worst in Greenbelt

She said that when an outside consultant tested the stream water as part of a study of the Greenbelt Lake watershed, completed in 2003, levels of nitrogen and phosphorus, from animal poop and fertilizer, exceeded U.S. Environmental Protection Agency guidelines.  The water also contained aluminum, copper, lead, oil and grease.  The firm rated the stream as the worst in Greenbelt.  That is why it was chosen for the project when funds became available, Hruby said.

The Maryland Department of the Environment gave Greenbelt a grant of $284,990 for the project.  Greenbelt Homes, Inc., gave $35,000, because the T-ball area near the stream is on their land.  The City put in the remaining $109,760.  Hruby said that the construction work costs about $350,000 and that when you add in planning and design work, it could end up costing about $500,000.

She said when the new headwall is installed it will have a new feature—the contractor, McDonnell Landscaping, Inc., will install a storm drain near Hillside Road that will funnel rain runoff from the road through the pipes and headwall to the stream, doing the job the old concrete chute used to do.

The Most Exciting Part

The most exciting part of the project, Hruby said, is what comes next: a "coastal plain outfall".  This is a fairly new technique that has been proven successful elsewhere, she said.  The plain includes rocks and eventually grasses and other plants to slow the stream down and intercept sediment and chemicals.  Hruby said the soil for the coastal plain is a precise mixture of compost and sand.

After the coastal plain comes a series of rock and gravel covered steps in the streambed, to also slow down the stream and reduce its erosive force, which has undercut the streambank in many places.  The project also involves replacing the first pedestrian bridge after the Hillside Road Underpass.  Right now, the stream is totally blocked by the bridge's wood foundation, with water flowing through two old corrugated pipes.  Hruby said that foundation and those pipes will be removed so the stream can flow freely and visibly under the new bridge, with rocks protecting the streambank from erosion.

Hruby said the project will not change the stream's center line, but will widen the banks to create a gentler slope.

The contractor will plant vegetation and replace each and every tree cut down, with trees and vegetation suited to streambanks.

The project should be finished soon, although cold weather could delay the plantings until spring, Hruby said.

The impervious surfaces in the neighborhoods near the stream contribute rain runoff to the streams, and with that runoff comes the oil spilled from oil changes and other chemicals and nutrients from neighborhood activities, Hruby said.  She added that the nutrients contribute to algae blooms on the lake.  

Hruby said part of the state grant money is for education, so the City will install signs explaining the design features.  They will also have rain barrel workshops and rain barrel giveaways, especially to people in the area. 

Nearby homes are where the pollution starts, the moment the first raindrop hits their roofs.